The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 17-50mm f2.8 XR II LD and the Canon 28-135mm f3.5-5.6 IS USM for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Canon 28-135mm f3.5-5.6 IS USM is the longer of the two lenses at 97mm. The Tamron 17-50mm f2.8 XR II LD with a length of 82mm, is 15mm shorter. Besides being longer, the Canon 28-135mm f3.5-5.6 IS USM also has a larger diameter of 78mm compared to the Tamron 17-50mm f2.8 XR II LD's 74mm diameter.
The weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Tamron 17-50mm f2.8 XR II LD weighs 430g, which means it is 110g (20%) lighter than the Canon 28-135mm f3.5-5.6 IS USM which has a weight of 540g.
Below you can find the dimension and weight table of the Standard Zoom Lenses in Canon EF Mount for size comparison purposes.
Standard Zoom Lenses in Canon EF Mount for Size Comparison
Lens Mounts
Both the Tamron 17-50mm f2.8 XR II LD and the Canon 28-135mm f3.5-5.6 IS USM has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon T8i, Canon 90D and Canon SL3.
Tamron 17-50mm f2.8 XR II LD is also available in Nikon F (DX) , Sony Alpha and Pentax KAF mounts.
Focal Range
Tamron 17-50mm f2.8 XR II LD has a focal range of 17-50mm and 2.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27.2-80mm when used on a APS-C / DX format camera. Canon 28-135mm f3.5-5.6 IS USM has a focal range of 28-135mm and 4.8X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 44.8 - 216mm.